There has been known acoustic wave devices using a piezoelectric substrate such as a lithium tantalate (LiTaO3) substrate. In such acoustic wave devices, a comb-shaped electrode is formed on the piezoelectric substrate. The comb-shaped electrode excites an acoustic wave on the surface of the piezoelectric substrate.
Japanese Patent Application Publication No. 3-3514 (Patent Document 1) discloses that the longitudinal direction of an acoustic wave device chip is made to be almost the cleaved surface of a lithium tantalate single crystal by using a lithium tantalate substrate with an X-plane.
The technique disclosed in Patent Document 1 can easily separate the substrate into individual chips because the longitudinal direction of the acoustic wave device chip is the cleaved surface. However, the plane direction of the disclosed technique is not suitable for mobile communication, and thus insertion loss of the acoustic wave device increases. On the other hand, problems may occur in separating the substrate into individual chips when a scribe line direction is determined in favor of characteristics of the acoustic wave device. For example, when the substrate is separated into individual chips by scribe and break, a cut surface meanders or inclines if the cleavage direction do not coincide with the scribe line direction. When the substrate is separated by dicing, production cost increases because supplies such as water and blades are used.